Rated pairwise preference ballot: Difference between revisions

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== Implementations ==
 
=== Rated or ranked preference ===
One particular, easier approach to implementing this generalized ballot type is to allow the voters to score the candidates on a scale, and also allow them to check a box indicating whether they have rated or ranked preferences. If using [[pairwise counting]], this can be counted by, for voters who indicate rated preferences, collecting their scores directly, and for those with ranked preferences, doing regular pairwise counting. For example, suppose the following information is collected:
{| class="wikitable"
Line 225 ⟶ 227:
|8.4
| ---
|}If using [[:Category:Condorcet-cardinal hybrid methods|Category:Condorcet-cardinal hybrid methods]], or any voting method where you want to store both the candidate's actual score and their support in head-to-head matchups, it is likely best to store the scores of each voter in one of two separate data values in each candidate's cells i.e. if a voter expressed a rated preference, put their score for a candidate only in the "rated preference" value, but if they expressed a ranked preference, put the score only in the "score for candidate" value. So, for example, a voter expressing a ranked preference who scored candidate A a 5 would be treated as giving A 0 points in the "rated preference" data value but 5 points in the "score for candidate" data value (which could be read as "0, 5" in the A>A cell). This would then be tabulated by giving each candidate as many points as they have in the rated preference data value i.e. a candidate with 51 points in the rated preference value and 37 in the score value would have those values treated such that, supposing a max score of 5, 51/5=10.2 votes would be added to all of their pairwise matchups in favor of them, and 51 points would be added to their score value to find that they have 88 points overall. This actually is easier to count than having to do pairwise counting with only ranked ballots, because for each voter who expresses a rated rather than a ranked preference, their support for a candidate in a head-to-head matchup can be summarized as one data value (the score for the candidate) rather than up to (number of candidates - 1) data values (i.e. the fact that they give that candidate 1 vote in each head-to-head matchup against a lower-ranked candidate).<blockquote>It's possible to modify Score to be more like a traditional Condorcet method by allowing voters to write the scores they would give to every possible pair of candidates in a Score runoff, and then using a Condorcet method to process this, treating a score of, say, A5 B3 (where the max score is 5) as 0.4 votes for A>B. As this would be utterly infeasible with just a few candidates running however, one way to accomplish most of the same objective is to allow voters to mark on their ballots that they want their vote strategically optimized, meaning that if their cardinally expressed preferences are A5 B3 Z2, instead of having their vote considered as B3 Z2 in an B vs. Z runoff, it would be considered as B5 Z0 (if the max score is 5), which is functionally equivalent to the Plurality voting runoffs that are used for the traditional Condorcet winner definition. This strategic optimization can be done fractionally to allow a voter to customize how much optimization they want to be done with their scores in each runoff. It is also possible for voters to indicate a preference threshold, meaning that for all preferred candidates, no strategic optimization is applied to pairwise matchups between them, but all other matchups are strategically optimized. With this modification, if all voters use strategic optimization, Score becomes a traditional Condorcet method (which will need a cycle resolution method to be applied at times), but if no voters strategically optimize, it remains Score (which never needs cycle resolution methods to be applied).</blockquote><blockquote>Note that when designing a ballot to allow voters to indicate strength of preference in pairwise matchups, it could be done by allowing the voters to rank or score the candidates themselves, and then indicate "between your 1st choice(s) and 2nd choice(s), what scores would you give to each in a pairwise matchup?" or "between the candidates you scored (max score) and the candidates you scored (max score - 1), what scores would you give in their pairwise matchups?", etc. Here is an example of one such setup: https://www.reddit.com/r/EndFPTP/comments/fcz3xd/poll_for_2020_dem_primary_using_scored_pairwise/<nowiki/> and some discussion: https://www.reddit.com/r/EndFPTP/comments/fimqpv/comment/fkkldcl?context=1</blockquote>
 
=== Preference threshold ===
<blockquote>It's possible to modify Score to be more like a traditional Condorcet method by allowing voters to write the scores they would give to every possible pair of candidates in a Score runoff, and then using a Condorcet method to process this, treating a score of, say, A5 B3 (where the max score is 5) as 0.4 votes for A>B. As this would be utterly infeasible with just a few candidates running however, one way to accomplish most of the same objective is to allow voters to mark on their ballots that they want their vote strategically optimized, meaning that if their cardinally expressed preferences are A5 B3 Z2, instead of having their vote considered as B3 Z2 in an B vs. Z runoff, it would be considered as B5 Z0 (if the max score is 5), which is functionally equivalent to the Plurality voting runoffs that are used for the traditional Condorcet winner definition. This strategic optimization can be done fractionally to allow a voter to customize how much optimization they want to be done with their scores in each runoff. It is also possible for voters to indicate a preference threshold, meaning that for all preferred candidates, no strategic optimization is applied to pairwise matchups between them, but all other matchups are strategically optimized. With this modification, if all voters use strategic optimization, Score becomes a traditional Condorcet method (which will need a cycle resolution method to be applied at times), but if no voters strategically optimize, it remains Score (which never needs cycle resolution methods to be applied).</blockquote>Example of this "preference threshold" idea with a single voter, using a rated ballot scale of 0 to 5 (threshold indicated with a "'''|'''"):<blockquote>A:5 B:4 | C:2 D:1</blockquote>This is converted into a pairwise table of:
{| class="wikitable"
|+
!
!A
!B
!C
!D
|-
|A
| ---
|1
|1
|1
|-
|B
|0.8
| ---
|1
|1
|-
|C
|0
|0
| ---
|1
|-
|D
|0
|0
|0
| ---
|}
The matchup between A and B is treated as weak because both candidates come before the threshold (i.e. the voter only gives 0.2 more votes to A than B, which is their scored preference of (5-4)/5=1/5th or 0.2 votes; keep in mind that when changing the scale from 0 to 5 to 0 to 1, the scores of 5 and 4 become 1 and 0.8 respectively, which is what you see in the pairwise table. It is also possible to put 0.2 and 0 instead, which captures only the margin and not the winning votes for the matchup), while all other matchups are treated as maximal (despite, for example, A>C only having a scored preference of (5-2)/5=3/5th or 0.6 votes, it is instead treated as a maximal preference of 1 vote).<blockquote>Note that when designing a ballot to allow voters to indicate strength of preference in pairwise matchups, it could be done by allowing the voters to rank or score the candidates themselves, and then indicate "between your 1st choice(s) and 2nd choice(s), what scores would you give to each in a pairwise matchup?" or "between the candidates you scored (max score) and the candidates you scored (max score - 1), what scores would you give in their pairwise matchups?", etc. Here is an example of one such setup: <ref>{{Cite web|url=https://www.reddit.com/r/EndFPTP/comments/fcz3xd/poll_for_2020_dem_primary_using_scored_pairwise/|title=r/EndFPTP - Poll for 2020 Dem primary using Scored Pairwise Matchups|website=reddit|language=en-US|access-date=2020-04-28}}</ref> and some discussion: <ref>{{Cite web|url=https://www.reddit.com/r/EndFPTP/comments/fimqpv/adjusting_pairwise_matchup_margins_to_favor/fkkldcl|title=r/EndFPTP - Comment by u/Chackoony on ”Adjusting pairwise matchup margins to favor higher-utility candidates”|website=reddit|language=en-US|access-date=2020-04-28}}</ref></blockquote>
 
== Notes ==
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The main voting methods with which this ballot type can be used in the single-winner case are the [[:Category:Pairwise counting-based voting methods]].
 
== References ==